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having cleaned quite a few intakes filled with carbon before, i don't think i would want to introduce EGR upstream of the throttle... it will gut stuck in the worst of places, including but not limited to your IAC system and likely on the throttle shaft itself...
you don't want either of those getting stuck open.
that and consider this: EGR flows largely due to differences in pressure.... pressure in the exhaust will always(with very few exceptions) be higher than pressure in the intake system. now, compare exhaust pressure to atmospheric pressure and while you will still have flow, compare exhaust pressure to manifold pressure... while atmospheric pressure will be around 100kPa at sea level, manifold pressure could be around 50kPa at cruising speeds. with EGR being introduced behind the throttle, the engine will literally be sucking exhaust into the engine, rather than it before before the throttle and the exhaust flowing in.
clear enough?
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